Silicone rubber-coated fiberglass fabrics, a type of silicone rubber flexible composite, and polytetrafluoroethylene (“PTFE”) coated and/or laminated fiberglass fabrics, a type of fluoropolymer composite, are commonly used in conveyor belts for diverse applications. These applications typically require composites that are flexible and thermally stable in operating environments exceeding 300° F. The composites must also possess a low-energy surface to ensure easy release of sticky, viscous, or adhesive materials. In some cases, the composite surface should have a high coefficient of friction, or other surface characteristics or modifications that will allow the belt to transfer lateral force to articles resting on, pressed against, or otherwise being conveyed by the belt.
Rubbers used in the construction of conveyor belts are generally considered to be relatively high-friction materials. However, the coefficient of friction between the surface of a typical conveyor belt made with silicone rubber-coated fabrics and the surface of objects contacting the belt is sometimes insufficient to prevent objects from slipping on the surface. Slippage can occur, for example, when the belt is used to carry objects up or down an incline, or when the belt is employed to provide lateral force to urge an object, slightly compressed between the conveyor belt and another surface, along that surface. In some applications, such as in cooking, dirt, grease, oil, or other contaminants deposited on the surface of the belt further reduce the coefficient of friction and increase the occurrence of slippage.
Ridges, ribs, lugs, or other protuberances may be configured into, or upon or attached to the surface of the conveyor belt to prevent objects on the belt from slipping. The protuberances applied to the surface are sometimes referred to collectively as a flight, and a conveyor belt so modified is called a flighted belt. The flight may consist of separately molded, extruded, or otherwise formed components attached to the belt with adhesives or mechanical fasteners, or the components may be molded into the surface of the composite. The latter operation entails the use of expensive and inflexible molding or embossing dies and equipment.
Flighted conveyor belts have been employed in the prior art for a variety of end uses. However, a flighted conveyor belt is not known in the art for use in a food cooking application wherein the belt is used to convey objects continuously through a heating zone of extremely high temperatures ranging from 250° F. to 525° F. At these high temperatures, belts presently used tend to mark or overly compress objects being cooked, giving the cooked objects an undesirable appearance.
For example, in a contact toaster device such as the one shown in U.S. Pat. No. 4,530,276, issued Jul. 23, 1985 to Dye O. Miller, a metal-linked conveyer belt conveys food objects, such as buns, along and against a heated platen to toast the buns. The buns may be marked by the heated belt or overly compressed against the platen resulting in an undesirable appearance. It would be desirable to create a conveyor belt that efficiently moves objects through a heating zone without marking or overly compressing the objects during cooking. Smooth silicone non-flighted belts available in the art are capable of eliminating markings, but do not exert sufficient lateral force to move food objects consistently and reliably along a heated platen, particularly as the belts become contaminated with grease and debris. Consequently, the food objects do not travel through the heating zone for the prescribed time, resulting in non-uniformity of the cooked product. The present invention was developed to overcome these deficiencies.
It is an object of the invention to provide modified flexible composites with integral flights. Another object of the invention is to provide a method for producing the flighted conveyor belts of the invention. It is an additional object of the invention to provide a flexible composite for use as a conveyor belt in a contact toaster for moving food items. The flexible composites of the invention may also be used as a conveyor belt cover in contact toasters wherein the conveyor belt cover is driven by a chain belt such that the ribs on the flighted face of the conveyor belt cover contact the chain belt and engage horizontal wire elements in the chain belt to reduce slippage between the conveyor belt cover and the chain belt.
It is further an object of the invention to provide a flexible composite for use as a conveyor belt in a vertically-oriented roll toasting machine wherein the conveyor belt contacts the outer, uncut surface of the roll halves, and provides lateral force to the rolls such that the rolls slide with their cut surface along a stationary, toasting surface, without producing indentations, markings or blemishes on the outer surface of the rolls.
It is a further object of the invention to provide a flexible composite for use as a conveyor belt in a food preparation or other device involving liquid flow wherein the conveyor belt comprises multiple ribs raised above the face of the belt that contacts the involved food or other article wherein the raised ribs control or direct liquid flow between the articles and the belt.
It is a further object of the invention to provide a flexible composite for use as a conveyor belt in a variety of devices, for example a semiconductor processing machine, wherein the conveyor belt comprises multiple raised ribs that control or direct the spacing or location of articles upon the conveyor belt in up to three dimensions.
A further object of the present invention is to provide a flexible composite for use as a conveyor belt in a variety of automated mechanical devices, for example, an automated mechanical conveyor machine, wherein the conveyor belt comprises multiple ribs raised above the face of the belt wherein such ribs mold, cut, shape, contain, or retain the articles upon the conveyor belt for use in moving the articles through an assembly operation.
A further object of the present invention is to provide a flexible composite for use as a texture producing belt in an architectural or other decorative/artistic application wherein the belt comprises multiple ribs raised above the face of the belt wherein such ribs directly or indirectly, through molding, offset, or transfer processes, provide architectural or decorative textures to a variety of materials for use in such applications.
A further object of the present invention is to provide a flexible composite for use as a production belt in a materials production process, wherein the production belt comprises multiple ribs raised above the face of the belt wherein such ribs include absorbers or susceptors of infrared, microwave, or radio frequency radiation or electrically conductive fillers allowing the ribs to be heated or otherwise energized so that they can be used to brand, mark, emboss, laminate, or otherwise impress or texturize appropriate materials for use in a wide array of applications, such as, for example, bubble packaging.
The conveyor belts of the invention are suitable for use in high temperature applications, and may be constructed of various composites, including fabric-reinforced silicone rubbers, urethane rubbers, or fluoropolymer, including fluoroplastics (such as PTFE) and fluoroelastomers, or blends thereof. The methods for making such flexible composites allow for flexibility in forming the shape, height and other characteristics of the flight. Advantageously, in cooking applications, conveyor belts of the invention and conveyor belts made of composites using the methods of the present invention provide a means for ensuring uniform time and temperature exposure of the object being cooked. In addition, such conveyor belts do not unduly mark or compress the object being conveyed through a zone of high temperature, are easily and quickly cleaned after use, and are relatively inexpensive to produce.